For the natural needs of domestic animals such as cats, it is customary to use litterboxes or containers for receiving solid and liquid excrement in a quantity of litter. To prevent odors and ensure cleanliness, the litter must be cleaned regularly and changed at regular intervals. Maintenance of the litter requires more or less daily attention by the pet owner. This continual maintenance is not only unpleasant, but inconvenient if the pet owner wishes to leave the house for an extended period of time.
A device for automatically separating solid excrement from used litter is shown, for example, in French Patent 2,556,621. This device generally comprises a hopper for dispensing litter onto a movable film, and a filter for covering used litter removed by the movable film. The solid excrement is separated from the litter by means of a grating, so as to be received in a collection chamber where it is stored, and periodically discharged. However, this device has a number of disadvantages. The device requires both a supply of litter and a supply of film, both of which must be maintained continuously. The device employs heavy and expensive mechanisms which are susceptible to malfunction, and there are difficulties in sealing off the litter granules from the drive mechanism. Furthermore, the litter is periodically discharged according to a time period which is determined by the user, leading to the disadvantage that the litter will be changed (completely) with each cycle of operation, whether the litter is soiled or not.